Cambridge Audio Azur 851W Power Amplifier


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Azur 851W Flagship Power Amplifier

The 851W is our flagship power amplifier, with immense power and incredibly low distortion. It’s perfectly matched to partner our 851E pre-amplifier and 851N network player; taking their pure signal and amplifying it with huge presence and authority. You’ll re-discover your favourite music in a quality that you’ve never heard before.


Rather than use a Class A design, which is sonically brilliant but generates vast amounts of heat, or a Class AB design, which is efficient but sonically limited, we developed our own Class XD amplifier design which the 851W takes advantage of. This has the sonic purity of Class A and the efficiency of Class AB for the best of both worlds.


When designing a stereo system, listeners are often encouraged to think about system matching, where components are handpicked to provide the best overall sound quality. People often assume this is due to the different audio characteristics, but frequently it is due to impedance (the relationship between voltage and current input/output) matching components. Products perform at their optimum when their input and output impedances match. This isn’t always possible though so we decided to develop our unique Terrapin impedance buffering module. This enables the 851W to be paired with a huge variety of audio sources and pre-amplifiers of varying impedance without risking any sacrifice in musicality or overall audio performance.


To build the 851W to be the best toroidal transformers were essential. But rather than use one for everything we designated one for the sound amplification itself, and another for the input circuitry. This means the signal is unaffected by audio output volume, so always sounds fantastic. The primary toroidal transformer provides unrestricted power to the dual mono amplification blocks. It’s a true audiophile transformer that will operate without distortion and with no buzz, interference or hum. The second smaller toroidal transformer takes care of pre-amplification processes. View the videos below for an insight on why we use toroidal transformers.

Technical specifications

  • Power output – stereo/mono 200W per channel into 8 Ohms 350W per channel into 4 Ohms
  • Power output – bridged mono 500W 8 Ohms 800W 4 Ohms
  • THD (unweighted) < 0.001% 1 kHz < 0.005% 20 Hz – 20 kHz
  • Frequency response 5Hz – 80kHz
  • S/N ratio (ref 1W / 8 Ohn)>90dB (unweighted)
  • Sensitivity – stereo or mono 1.5V rms unbalanced 1.5 + 1.5V rms balanced
  • Sensitivity – bridged mono 0.775V rms unbalanced 0.775V + 0.775V rms balanced
  • Input impedances Balanced input 38 kOhm Unbalanced input 68 kOhm
  • Power amp damping factor> 110 at 1 kHz
  • Max. power consumption 2400W
  • Standby power consumption Standby <0.5W
  • Colour Black or silver
  • Dimensions (HxWxD)148 x 430 x 365mm (5.8 x 16.9 x 14.4”)
  • Weight 19.1kg (42.2lbs)


Additional information


Cambridge Audio




Black, Silver